Rocket recoil

[Sundowner.pl]

3) But, if you look closely at the video

after 1.50 to 1.59, which shows the pilots in the cockpit, it is clearly seen that even while firing two rockets helicopter shakes.

The shake is caused by shifting CofG, and the angular force applied by the rocket - it starts to spin inside the launcher, and the slight off-axis thrust vector make it transfer some force to the sides of launcher tube.

 

Finally, when I have employ rockets with a MI-8 in salvo 32 (8 from each launcher), the 11 tonn Mi-8 had reduced speed at 200 km / h to 180 ... 185 km / h, the direction of flight changed by about 10 degrees, and the pitch helicopter (nose) had gone up to about 5 degrees.

Here's my question - how much mass was dumped by firing 32 rockets, changing the CofG ? I would hazard a guess, that if you dropped a 160-480 kg load (were they S-5 or S-8 rockets?) you would see the same shift in CofG, making the helicopter lighter - less power required, so it will reduce torque - moving the nose sideways and rise the nose - which in result will drop the forward speed.

 

 

PS more, pay attention, how to construct the rear side of the launcher (see att.)

Here's the problem, that launcher is an M158A1, it was designed to work with rockets with Mk4 and Mk40 rocket motors, those are of different design having four distinct nozzles, and fins stowed behind them - separating them, those fins are held together by a piece of plastic with conductive material which is pushed against those studs you see on the aft end of the launch tubes. When the Mk4/40 rocket launches, the gases are funneled around those studs, so the don't transfer any force directly (friction, boundary effect). Now in game you made the launcher shoot Mk66 rocket motor Hydra 70 rockets, if you try to load them into that launcher that stud will go well inside the exhaust nozzle blocking it, leading to rocket explosion at ignition*. Plus the rocket is not retained in those launchers tubes, by any other means than the spring loaded fins pushing against the inside of the tube.

 

* - you can't actually ignite the Mk.66 rocket inside of the M158 or M159 launchers - the igniter contact is on the rocket circumference, not only centrally in the back where the only igniter contact is on those old launchers.

Edited May 29, 2013 by Sundowner.pl

[Focha]

So can anyone from Belsimtek share their opinion on this? Been following this and as Sundowner told, not one has guaranteed us that those will be fixed. Since I pay a huge amount of money for this aircraft sim I would also like to see some opinion on the future of the Huey.

[Griffin]

PilotMi8 is the main guy from Belsimtek AFAIK.

[Suchacz]

Some vids of Huey rocket fire, IMHO no significant recoil can't be seen.

 

[159th_Falcon]

guys! Maybe we can calculate not very accurately, however:

1) When you shoot one or two rockets really not visible recoil

2) Also, when you look from the side - not visible recoil

3) But, if you look closely at the video

after 1.50 to 1.59, which shows the pilots in the cockpit, it is clearly seen that even while firing two rockets helicopter shakes.

Finally, when I have employ rockets with a MI-8 in salvo 32 (8 from each launcher), the 11 tonn Mi-8 had reduced speed at 200 km / h to 180 ... 185 km / h, the direction of flight changed by about 10 degrees, and the pitch helicopter (nose) had gone up to about 5 degrees.

Maybe launch a 70-mm rockets from the XM158 or XM159 associated with less recoil, maybe...And it can be configured easily, but need information from practice. This information must be much more accurate than the video shown here (ie in numbers).

PS more, pay attention, how to construct the rear side of the launcher (see att.)

1) there is in sim, at least when firing a pair of rockets. (1 each side)

2) as above

3) That the helicopter shakes is to be expected, shaking is quite different from a violent change in Pitch though.

A salvo of 38 rockets is bound to have an impact if it wasn't simply for a change of overall weight and CoG, like Sundowner.pl explained.

And as you mention, the pitch of the Mi-8 went up, Huey in sim goes down

(99% sure)

 

Also, to clarify, not posting all this to make the Huey or Belsimtek look bad.

More like trying to help and point out an issue.

 

Cause so far, you guys made one hell of a simulator that's great fun to play.

And i have only two real issues whit it at the moment.

 

The rocket recoil discussed here

 

If you move to any of the moving gun position's Track IR is default way to control them.

Which sucks, in my opinion at least.

Maybe ad an option under the special settings tab?

Gun position controlled by Track IR / Mouse. And let user select preference?

[ericoh]

There is definetely a recoil from the rockets... Also i dont seem to get that "several degrees" of angle changes that some people here talk about.

[SimFreak]

There is no such thing as recoil-less....

 

"Law III: To every action there is always an equal and opposite reaction"

 

It's the law....

[Sundowner.pl]

What is the action, and what is the reaction here ?

 

THINK

 

A lot of expanding gases are produced in compartment with one exit - those gases are released by that exit - it's a lot of mass going one direction - this is the action. The reaction is the projectile in which this action is taking place, being moved by equal force the opposite way.

 

Where's the helicopter, or even the launcher in this ? It's a ROCKET, the RECOIL is what's acting on the PROJECTILE, not launcher or helicopter. Are we really going to continue through 4th page of discussion about a failure in basic physics ?

Edited May 29, 2013 by Sundowner.pl

[SimFreak]

how much force is required to remove that rocket? what is Fr?

What about ignition system? is that in a way of a blast?

 

*PS, I'm armchair export on this subject. Helllfire...yes. Not this system

[Sundowner.pl]

how much force is required to remove that rocket?

what is Fr?

You know that vectors from both forces will be directed forward, not back right ?

 

What about ignition system? is that in a way of a blast?

Yes and no. As I posted earlier, you can't fire Mk66 rocket engine from M158A1 launcher pod - there is no igniter connection, if there would be, then yes, the ignition arm would be in the way... actually it would be blocking the nozzle, increasing internal pressure in combustion chamber, resulting in explosion. Now for Mk4 and Mk40 rocket engine, for which that particular launcher was designed for - no, it's not in the way, since the gases are directed around it.

[Eight Ball]

 

At 16:20 the door gunner says : "(...) If you'd shot all 48 you'd back up 20 feet (...)"

So it seems those rockets produce a noticeable recoil.

Edited June 1, 2013 by Eight Ball

[Sundowner.pl]

Quote the whole thing, because he doesn't talk about horizontal, but vertical. 48 Mk4 rockets from XM3 subsystem - that's 1008 lb of ballast thrown overboard. In a helicopter that has 3000lb of total useful weight - that's considerable amount.

[AirwolfPL]

I agree that FFARs have too much recoil. But it's not like they shouldn't have any effect on the chopper whatsoever. I remember a chat with the Mi-24 pilot who stated that a salvo of multiple (I don't remember exact number) of unguided rockets could significantly slow down the chopper and set it off course. Some years ago I also talked to a former military Mi-2 pilot (which is in fact easier to compare with the UH-1) who said that a unguided rocket salvo could stop the chopper mid-air (I think he was exaggerating a bit though). But in fact when I was desiging OFP addons (Mi-2 addon in particular) I've seen some videos of Mi-2 rocket attacks and it presented similar behaviour to this of DCS's UH-1 (on the other hand russian launchers have a pretty dense perforated sheet of metal on the rear of the launcher, behind the rocket's exhaust which may have something to do with that).

[scrtagnt69]

The recoil from a rocket is fairly accurate depending on the amount fired at one time 48 max it would push the UH-1 approx. 20 feet in reverse in real life.Most pilots chose to shoot single or double pairs at a time saying that the effect of the aircraft being pushed backwards was a very scary feeling even though they were in the middle of a hot AO with tracers all around.

[Kuky]

There should be no recoil, well it should be absolute minimal one, but I wouldn't call it a recoil because only 2 forces can act on launcher tubes and the chopper and that is bit of friction as rocket leaves the tube, and some air pressure as rocket left the tube... the friction force should be pulling the tube in same direction as rocket (forward) and the gases that hit the tube/pod as rocket leaves the tube are pushing it backwards.

 

As the tubes are lower than rotors on which the chopper is "hanging" from, what should happen is friction should pull the tube making helicopter pitch up slightly, then as gases hit the front of the tube there will be some force in opposite direction and helicopter should experience pitch down. But considering that friction force should not be much (otherwise it will affect performance and range of the rocket) and gases do disperse and slow down very rapidly, both forces should be very minor... considering the much much greater mass of the helicopter, really I don't see this recoil effect being so much at all.

[Suchacz]

The friction between the rocket and its tube is minimal, those rockets are loaded by bare hand.

[BIGNEWY]

LQE4zdvbVdc

 

just came across this only a short clip, and one rocket fired.

 

slight recoil ? difficult to tell

[Suchacz]

Mi-24 rocket live fire exercise. You can see some vibrations on the video, but it is hard to see some movement caused by the recoil. I know, that Hind is much heavier than Huey...

Edited November 8, 2013 by Suchacz

[scrtagnt69]

Every veteran gunship pilot has told me the same thing when you felt the thump it was a good shot if there was no thump it meant the rocket was jammed and now they were flying with a live bomb attached to the GS...from what I understand the thump felt was the recoil from the rocket..I will ask Steve "Razor Back 33" Bookout to elaborate.

[Krebs20]

Lets think of this in game only. The rocket is fired. The helicopters CG is affected. The flight model reacts. We get angry.

 

Now take the limitations on our real sim hardware. A short joystick that is more accurate than most of us are able to fly, trying to replicate a real cyclic that's longer and less precise. The real thing just has the advantage of feedback.

I have found that with a longer sim cyclic and FFB, the recoil effects are dramatic reduced.

Simulations has an issue in being perfect. What I mean is that even though physics say that a change in CG means x will happen, in real life it just doesn't. Aerodynamics of a moving helicopter are very complex it turns out. This is the limitation in sim software.

If you want something entertaining to do, I suggest loading one side with rockets only. Try to fly the Huey and maintain the course with a CG imbalance on your rocket run.

 

Im Sorry I have no answers on this issue. But try to think about what it really happening vs posting a YouTube vid that looks good.

[Suchacz]

Im Sorry I have no answers on this issue. But try to think about what it really happening vs posting a YouTube vid that looks good.

Thats the point. We have no voodoo to discuss here, we simply need some relevant numbers, not some uneducated guesses :smilewink:

[scrtagnt69]

" When you punch off 2.75"s, they have a tendency to slow the aircraft down noticeably."

Steve " Razor Back 33 " Bookout.

120th AHC/VN 68-72

 

Just got done chatting with Steve and I asked if the firing of rockets change the handling this was his answer..I have faith in his word..He is the only pilot to ever have Gen.Westmoreland as a peter pilot on multiple missions as well as John Wayne as a door gunner (Strap Hanger) on 2 missions..Living Legend..

[Kuky]

^^^

 

He needs to define "noticeably".... how much speed (in numbers) we are talking about? If I am looking at speedo and I fire some weapon and I see speed drops 1-2 kmph... then I can define that as noticeable speed drop (because I can see it, notice it)... but if I am not looking at speedo and I do the same... most likely you will not notice it... well if you are fully stationary and you see you've moved a notch then again, you would notice it.

 

Still the one thing you must trust it the physics of it... someone saying something from their own feeling/undrstanding/seeing is one thing, but if proven science says it is so, then it is so.

[scrtagnt69]

[AlphaOneSix]

So today at lunch I decided to pose this question to some of my coworkers.

 

No recoil.

 

This is from an OH-58D pilot and a DAP pilot and a DAP crew chief.